The present invention relates to motor vehicle sensors and actuators.
To comply with state and federal environmental regulations, most motor vehicles are now equipped with a carbon canister installed to trap and store petroleum fuel vapors from the fuel system. With the canister, fuel vapor is not vented to the atmosphere, but instead is trapped in the canister and then periodically purged from the canister into the engine where the fuel vapor is burned along with the air-fuel mixture.
Solenoid valves have been provided that are used to purge the fuel vapor from the carbon canister. Unfortunately, many of these valves are adversely affected by signal noise caused by contact between the plunger and its corresponding stop or a lack of material for absorbing the impact between the plunger and the stop. Moreover, oxidation within the typically deep spring pocket can lead to failure of the valve.
The present invention has recognized these prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
A solenoid valve includes an outlet tube and a plunger assembly. The plunger assembly includes a plunger stop and a plunger. The plunger is movable between a closed position wherein the plunger engages the outlet tube to block fluid flow through the valve and an open position wherein the plunger is distanced from the outlet tube to permit fluid flow through the valve. Moreover, the plunger is stopped by the plunger stop and includes a plunger stop cushion to cushion impact between the plunger and the plunger stop.
Preferably, the plunger stop cushion is dome-shaped. Furthermore, in a preferred embodiment, the plunger forms a bore and includes a plunger insert disposed therein. Preferably, the plunger insert includes a proximal end plug that forms the dome-shaped plunger stop cushion. Additionally, the plunger stop forms a flat plunger
contact face that contacts the plunger stop cushion when the valve is moved to the open position. In a preferred embodiment, the valve includes a coil that is energizable to bias the plunger from the closed position to the open position. A spring biases the plunger from the open position to the closed position. Preferably, the outlet tube is circumscribed by a valve seat and the plunger insert includes a distal end cap that engages the valve seat when the valve is in the closed position. The distal end cap is connected to the proximal end plug by a stem through the plunger.
In another aspect of the present invention, a solenoid valve includes an outlet tube and a plunger stop disposed stationarily relative to the tube. A plunger is disposed within the solenoid valve between the outlet tube and the plunger stop. The plunger is movable between a closed position and an open position. In the closed position, the plunger engages the outlet tube to block fluid flow through the valve and is distanced from the stop. In the open position, the plunger is distanced from the outlet tube and abuts the stop to permit fluid flow through the outlet passage. The plunger also includes a plunger stop cushion that contacts the plunger stop when the valve is opened.
In yet another aspect of the present invention, a solenoid valve includes outlet means and plunger stop means. The solenoid valve also includes plunger means that is movable between a closed position, wherein the plunger means engages the outlet means to block fluid flow through the valve, and an open position, wherein the plunger means is distanced from the outlet means to permit fluid flow through the valve and the plunger means is stopped by the plunger stop means. In this aspect, the plunger means includes means for cushioning impact between the plunger means and the plunger stop means.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: